1. Field of the Invention
The present invention relates generally to medical devices, systems, and methods. More particularly, the present invention relates to tools, systems, and methods for delivering compliant fasteners and compression structures for tissue approximation, for example to isolate left atrial appendages and other tissue structures near their bases.
Atrial fibrillation is a relatively common condition characterized by a very rapid heart beat of the left and right atrium. While atrial fibrillation is not normally fatal itself, it has been associated with an increased risk of stroke. It is believed that the rapid heart beat causes blood to pool in the left atrial appendage which causes emboli that are released into the left atrium from where they can enter the cerebral vasculature, thus causing a stroke. In addition to stroke, the emboli can enter coronary circulation, potentially causing myocardial infarction, or can enter peripheral circulation, potentially causing peripheral vascular disease.
The risk of stroke in patients suffering from atrial fibrillation can be reduced in a variety of ways. For example, blood thinning drugs can be used to reduce the risk of clot formation. The use of blood thinners, however, is contraindicated in patients at risk of bleeding disorders.
More aggressive treatment protocols have been proposed which involve closing the left atrial appendage. Closure and excision may be performed in open surgical procedures, typically requiring the patient to be placed on by-pass and the chest to be opened through the sternum. Alternatively, thoracoscopic and other less invasive procedures have been proposed. U.S. Pat. No. 5,306,234 teaches the performance of beating heart procedures using otherwise conventional surgical techniques. The use of conventional techniques through small chest penetrations while the heart is beating can be difficult to perform. U.S. Pat. No. 5,865,791 describes an intravascular approach where tools are introduced through the vasculature and passed into the left atrium. The tools are used to ablate or fuse the left atrial appendage from the inside using energy, adhesives, or the like. The '791 patent also describes a thoracoscopic procedure where a tether is placed over the neck of the atrial appendage and tied off to achieve isolation. The '791 patent still further suggests other closure elements including sutures, staples, shape-memory wires, biocompatible adhesives, and the like. U.S. Pat. No. 6,488,689 describes a transpericardial procedure where the distal tip of the left atrial appendage is grasped and pulled backwardly through a capture loop which encircles the base of the left atrial appendage.
Of particular interest to the present invention, a compliant closure structure for the sealing of the left atrial appendage is described in co-pending, commonly owned U.S. Patent Publication 2007/0260278 (application Ser. No. 11/744,135), the full disclosure of which has been previously incorporated herein by reference. The compliant structure described in the '135 publication comprises an elastomeric body having a pair of opposed legs which may be arranged in an oval or a U-shaped configuration to define an opening therebetween. By placing the opening between the legs over the left atrial appendage and aligning it with the base of the appendage, the structure may be closed to provide the desired sealing. To hold the structure closed, a number of discrete, axially spaced-apart tissue penetrating fasteners are arranged along the lengths of each of the legs. By compressing the legs together to press-fit the fasteners, the compliant structure may be closed to provide a compliant seal which effectively isolates the left atrial appendage.
U.S. Patent Publication 2007/0260278 describes a particular delivery tool for the compliant closure structure. The delivery tool includes jaws which can be inserted into the legs of the closure structure and actuated to close the jaws in the legs over the left atrial appendage. The jaws further include comb studs which engage and press fit the fasteners in order to hold the compliant structure in its closed, sealing configuration. The studs are intended to be retracted to allow the delivery tool to be removed.
Although functional, the delivery tool of the '135 publication has certain shortcomings. For example, the actuation of the jaws and retraction of the comb studs can be performed out of order, increasing the risk that the delivery of the compliant structure will fail. Moreover, positioning and orientation of the delivery tool can be difficult, particularly when the tool is introduced through an intercostal penetration to access the left atrium. Additionally, the jaws in the device of the '278 publication are attached in the axial plane of the device shaft. Such a straight line of attachment can make it more difficult to align the jaws with the base of the appendage and across the os of the atrium leading into the appendage. If the closure device is not aligned across the base to completely close the os, gaps or openings (referred to as “cul-de-sacs”) can remain at the site of closure, increasing the risk of thrombus formation in the atrium. The importance of forming a complete seal of the os which is free from such cul-de-sacs is discussed in Salzberg et al. (2008) Eur. J. Cardiothoracic Surg. 34:766-770.
For these reasons, it would be desirable to provide improved delivery tools for use with the tissue closure devices described in U.S. Patent Publication 2007/0260278. It would be further desirable if the delivery tools and methods of their use were compatible with the delivery of other tissue closure devices and for procedures in addition to closure of the left atrial appendage. At least some of these objectives will be met by the inventions described hereinbelow.
2. Description of the Background Art
Less invasive and other procedures for closing the left atrial appendage are described in U.S. Pat. Nos. 6,488,689; 5,865,791; and 5,306,234; and Published Application Nos. 2005/0154404 and 2004/0030335. Other tissue ligation tools and related devices and techniques are described in U.S. Pat. Nos. 6,790,172; 6,436,108; 6,325,810; 6,273,897; 6,051,003; 5,964,774; 5,624,453; 5,507,797; and 4,257,419. See also U.S. Patent Publication 2007/0260278 described above.